Impact of Diabetes Mellitus on Benefit of β-Blocker Therapy After Myocardial Infarction

Abstract

Beta blockers are uniformly recommended for all patients after myocardial infarction (MI), including those with diabetes mellitus (DM). This study assesses the impact of β-blocker type and dosing on survival in patients with DM after MI. A cohort of 6,682 patients in the Outcomes ofBeta-blockerTherapyAfter MyocardialINfarction registry were discharged after MI. In this cohort, 2,137 patients had DM (32%). Beta-blocker dose was indexed to the target daily dose used in randomized clinical trials and reported as percentage. Dosage groups were: no β blocker, >0% to 12.5%, >12.5% to 25%, >25% to 50%, and >50% of the target dose. The overall mean discharge β-blocker dose in patients with DM was 42.7 ± 34.1% versus 35.9 ± 27.4% in patients without DM (p <0.0001). Patients with DM were prescribed carvedilol at a higher rate than those without DM (27.8% vs 19.6%). The 3-year mortality estimates were 24.4% and 12.8% for patients with DM versus without DM (p <0.0001), respectively, with an unadjusted hazard ratio=1.820 (confidence interval 1.587 to 2.086, p <0.0001). Patients with DM in the >12.5% to 25% dose category had the highest survival rates, whereas patients in the >50% dose had the lowest survival rate among patients discharged on β blockers (p <0.0001). In the multivariable analysis among patients with DM after MI, all β-blocker dose categories demonstrated lower mortality than no therapy; however, only the >12.5% to 25% dose had a statistically significant hazard ratio 0.450 (95% confidence interval 0.224 to 0.907, p=0.025). In patients with DM, there was no statistically significant difference in 3-year mortality among those treated with metoprolol versus carvedilol. In conclusion, our analysis in patients with DM after MI suggested a survival benefit from β-blocker therapy, with no apparent advantage to high- versus low-dose β-blocker therapy; although, physicians tended to prescribe higher doses in patients with DM. There was no survival benefit for carvedilol over metoprolol in patients with DM.